Threading tool and method for bond wire capillary tubes

ABSTRACT

A capillary threading tool is used to thread bond wire through the capillary tool of a wire bond machine. The capillary threading tool includes a handle that is grasped to manipulate a body portion into a gap between the upper end of the capillary tube and the lower end of a guide tube that is positioned above the capillary tube. The body portion includes a guide surface that is placed in contact with the wire bond machine, and a vertical slot extending from the guide surface that terminates in a closed end having an inclined surface. The length of the slot is selected to position the lower edge of the inclined surface above the end of the capillary tube so the bond wire can be threaded into the capillary tube simply by forcing the end of the wire on the inclined surface.

TECHNICAL FIELD

[0001] This invention relates to integrated circuit fabrication, and,more particularly, to a method and tool to facilitate threadingintegrated circuit bond wires through capillary tubes in wire bondmachines.

BACKGROUND OF THE INVENTION

[0002] Wire bond machines are typically used to attach bond wiresbetween bond pads fabricated on integrated circuit dies and leadframesthrough which signals and power are routed to and from the integratedcircuit. A typical wire bond machine 10 is shown in FIG. 1. The wirebond machine 10 includes a spool 12 of bond wire 14, which is typicallygold wire having a diameter of about 1 mil (10⁻³ inches). The wire 14extends over a diverter 20 and passes through a housing 22 containing asensor 24 and an air guide 26. The sensor 24 and air guide 26 cooperatewith each other in a conventional manner to draw the wire 14 from thespool 12 and maintain the wire 14 at the proper tension. The wire 14then extends downwardly and passes through a nozzle 30 having arelatively large diameter to a guide tube 34, which also has arelatively large diameter. The guide tube 34 has a flared upper end 36that facilitates the threading of the wire 14 into the tube 34. The wire14 then extends through a gap 38, typically 0.5-1.0 inches wide, andpasses through a capillary tube 40 before reaching a bond head (notshown). The capillary tube 40 typically has a diameter of about 3.0-3.5mils. The capillary tube 40 is attached to a front panel 42 of the wirebond machine 10 by a clamp 44, which is secured to the front panel 42 bya pair of bolts 46 or other fasteners.

[0003] In operation, it is occasionally necessary to thread the bondwire 14 from the spool 12 to the capillary tube 40 such as, for example,if the supply of wire 14 from the spool 12 has been exhausted or thewire 14 breaks. Threading the wire 14 over the diverter 20 and throughthe housing 22 is fairly easy. Threading the wire 14 through the nozzle30 and guide tube 34 is somewhat more difficult, but because of therelatively large diameters of the nozzle 30 and guide tube 34, cangenerally be accomplished by a skilled operator fairly easily inrelatively little time. However, it is substantially more difficult tothread the wire 14 into an end 48 in the capillary tube 40 because ofthe relatively small diameter of the capillary tube 40. The guide tube34 is somewhat effective in guiding the wire 14 to the general vicinityof the end 48 of the capillary tube 40, but, because of the gap 34, thewire 14 is easily deflected from the entrance to the capillary tube 40.For example, there may be air currents present that, although slight,are sufficient to deflect the wire 14 away from the end 48 of thecapillary tube 40. Even the breath of an operator threading the wire 14can be sufficient to deflect the wire 14 away from the end 48 of thecapillary tube 40. As a result, it is invariably necessary for theoperator to manually guide the wire 14 into the end 48 of the capillarytube 40.

[0004] The operator typically guides the wire 14 into the end 48 of thecapillary tube 40 by grasping the wire 14 with a tweezers (not shown)while viewing the end of the wire 14 through a magnifier (not shown),such as a microscope (not shown). Successfully guiding the wire 14 intothe end 48 of the capillary tube 40 in this manner requires a great dealof skill and manual dexterity, and usually requires a great deal oftime. During the time the operator is threading the wire 14 through thecapillary tube 40, the bond machine 10 may not be used for fabricatingintegrated circuits. The difficulty in threading the wire 14 through thecapillary tube 40 not only results in excessive down-time of the bondmachine 10, but may also cause excessive down-time of an integratedcircuit fabrication line in which the wire bond machine 10 is used.Further, the skill required to manually thread the wire 14 through thecapillary tube 40 reduces the availability of operators capable ofoperating the wire bond machine 10 and, because manually dexterity andvision may decline with age, may shorten the careers of such operators.

[0005] There is therefore a need for a device and method to facilitatethe threading of bond wires through capillary tubes, thus reducing thetime and skill level required to thread bond wires through a bondmachine.

SUMMARY OF THE INVENTION

[0006] A capillary threading tool is used with a wire bond machine tothread bond wire in though a capillary tube positioned below a guidetube by a gap. The capillary threading tool includes a handle connectedto a body portion that is inserted into the gap. The body portionincludes a slot through which the bond wire passes between the guidetube and capillary tube. The slot has first and second portionsseparated from each other along the length of the bond wire. The firstportion of the slot has a width that is smaller than the outsidediameter of the capillary tube, and the second portion of the slot has awidth that is approximately equal to the outside diameter of thecapillary tube. The body portion is placed in the gap with the capillarytube inserted into the second portion of the slot beneath the firstportion of the slot so that the first portion of the slot substantiallyfills the gap. The first and second portions of the slot terminate inrespective first and second slot ends that are substantially alignedwith each other. The capillary tube is placed against the end of thesecond portion of the slot to align the end of the first portion of theslot with the capillary tube. As a result, the end of the first portioncan be used to guide the bond wire into the capillary tube.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007]FIG. 1 is a schematic view of a conventional wire bond machine.

[0008]FIG. 2 is an isometric view of a capillary threading toolaccording to one embodiment of the invention.

[0009]FIG. 3 is a side elevational view showing the capillary threadingtool of FIG. 2 in use on a wire bond machine.

[0010]FIG. 4 is a top plan view showing the capillary threading tool ofFIG. 2 in use on a wire bond machine.

[0011]FIG. 5 is a cross-sectional view taken along the line 5-5 of FIG.3.

DETAILED DESCRIPTION OF THE INVENTION

[0012] One embodiment of a capillary threading tool 50 for guiding bondwires 14 into capillary tubes 40 according to the present invention isshown in FIG. 2. The capillary threading tool 50 includes a body portion52 from which a cylindrical handle 54 projects. The body portion 52includes a first guide surface 60, a horizontal slot 62, and a verticalslot 64.

[0013] The capillary threading tool 50 is shown in use with the wirebond machine 10 in FIGS. 3 and 4. The capillary threading tool 50 ismanipulated by grasping the handle 54 to insert the tool 50 into the gap38 between the capillary tube 40 and the guide tube 34. As best shown inFIG. 3, the horizontal slot 62 provides clearance for the clamp 42 andbolts 44 that secure the capillary tube 40 to the wire bond machine 10.The horizontal slot 62 also divides the body portion 52, as well as thevertical slot 64, into a first, upper portion 66 and a second, lowerportion 68. As best shown in FIG. 4, the vertical slot 64 provides aremoval path for the bond wire 14 to allow the capillary threading tool50 to be removed after the bond wire 14 has been threaded through thecapillary tube 40. The lower portion 68 of vertical slot 64 preferablyhas a width that is just slightly larger than an outer diameter of thecapillary tube 40 so that the lower portion 68 of the vertical slot 64can straddle the capillary tube 40. The lower portion 68 of the verticalslot 64 can therefore fixes the transverse position of the body portion52 relative to the capillary tube 40.

[0014] The upper portion 66 of vertical slot 64 preferably has a widththat is smaller than an outer diameter of the capillary tube 40. As aresult, a second guide surface 70 formed by the upper surface of thehorizontal slot 62, i.e., the surface beneath the upper portion 66 ofthe vertical slot 64, rests against the end 48 of the capillary tube 40.The second guide surface 70 thus fixes the vertical position of the bodyportion 52 relative to the capillary tube 40. The height of the upperportion of the body portion 52 preferably corresponds to the size of thegap 38 (FIG. 1) between the guide tube 34 and the capillary tube 40 sothat there is no significant gap between the body portion 52 and theguide tube 34.

[0015] The position of the body portion 52 relative to the capillarytube 40 along the length of the vertical slot 64 should also be fixed toaccurately guide the bond wire 14 into the end 48 of the capillary tube40. In one embodiment, the distance between the first guide surface 60and a closed end 72 of the upper portion 66 of the vertical slot 64corresponds to the distance between the front panel 42 of the wire bondmachine 10 and the capillary tube 40. As a result, when the first guidesurface 60 is placed in contact with the front panel 42 of the bondmachine 10, the closed end 72 of the slot 64 is substantially alignedwith the capillary tube 40. In another embodiment, a third guide surface76 formed at a closed end of the lower portion 68 of the vertical slot64 is positioned so the capillary tube 40 will be aligned with theclosed end 72 when the capillary tube 40 is placed in contact with thethird guide surface 76. Therefore, either the first guide surface 50 orthe third guide surface 76 fixes the position of the body portion 52 ofthe capillary threading tool 50 along a longitudinal axistoward-and-away from the wire bond machine 10.

[0016] By fixing the closed end 72 of the vertical slot 64 so that it isin substantial alignment with the end 48 of the capillary tube 40, theclosed end 72 can be used to guide the bond wire 14 into the end 48 ofthe capillary tube 40 by simply guiding the wire 14 into the guide tube34. The bond wire 14 then exits the guide the guide tube 34 at theclosed end 72 of the vertical slot 64 and is then directed into thecapillary tube 40. To further facilitate the proper positioning of thebond wire 14 along the length of the vertical slot 64 an inclinedsurface 78 is formed at the closed end 72, as best shown in FIG. 5. As aresult, it is only necessary to manipulate an end of the bond wire 14 sothat it is positioned at some point on the inclined surface 78. Thevertical slot 64 and the inclined surface 78 then guide the wire 14 intothe end 48 of the capillary tube 40.

[0017] The capillary threading tool 50 allows even relatively unskilledoperators of the wire bond machine 10 to easily and quickly threaded thebond wire 14 through the capillary tube 40. Although specific structuresfor the wire bond machine 10 and the capillary threading tool 50 havebeen shown in FIGS. 1-5, it will be understood that a capillarythreading tool according to the invention can be used with other wirebond machines, and doing so may require some alteration of the size,shape and components of the capillary threading tool 50 shown in FIGS.2-5. Therefore, it will be appreciated that, although specificembodiments of the invention have been described herein for purposes ofillustration, various modifications may be made without deviating fromthe spirit and scope of the invention. Accordingly, the invention is notlimited except as by the appended claims.

1. A capillary threading tool for use with a wire bond machine having acapillary tube positioned below a guide tube, the capillary threadingtube comprising: a handle; and a body portion connected to the handle,the body portion having formed therein a first slot lying in a planeformed by first and second orthogonal axes, the first slot having firstand second portions separated from each other along the first axis, thefirst portion of the first slot having a width that is smaller than anoutside diameter of the capillary tube, and the second portion of thefirst slot having a width that is at least as large as the outsidediameter of the capillary tube, the first portion of the first slothaving a dimension along the first axis that is less than a distancebetween the guide tube and the capillary tube.
 2. The capillarythreading tool of claim 1 further comprising an inclined surface formedat an end of the first portion of the first slot, the inclined surfacesloping inwardly from the end of the first portion of the first slot. 3.The capillary threading tool of claim 2 wherein the inclined surfacecomprises an inclined plane.
 4. The capillary threading tool of claim 1wherein the wire bond machine further comprises a vertical surfacepositioned adjacent to the capillary tube a first distance from thecapillary tube, and wherein the first portion of the first slot has adepth extending from a first surface of the body portion to a slot endthat is substantially equal to the first distance.
 5. The capillarythreading tool of claim 1 wherein the wire bond machine furthercomprises a vertical surface positioned adjacent to the capillary tube,and wherein the first portion of the first slot has a depth selected sothat when a first surface of the body portion is placed in contact withthe vertical surface of the wire bond machine, a slot end of the firstportion of the first slot is positioned in substantial alignment withthe capillary tube.
 6. The capillary threading tool of claim 1 furthercomprising a second notch extending through the body portionperpendicularly to the first slot between the first and second portionsof the first slot.
 7. The capillary threading tool of claim 1 whereinthe width of the second portion of the first slot is substantially equalto the outside diameter of the capillary tube.
 8. The capillarythreading tool of claim 1 wherein the first portion of the first slotterminates in a first slot end, and the second portion of the first slotterminates in a second slot end that is substantially aligned with thefirst slot end so that the first slot end is substantially aligned withthe capillary tube when the capillary tube is in contact with the secondslot end.
 9. A capillary threading tool, comprising: a handle; and abody portion connected to the handle, the body portion having formedtherein a first slot opening at a first surface of the body portion, asecond slot opening at the first surface of the body portion, the secondslot being perpendicular to the first slot to divide the first slot intofirst and second slot sections that terminate at respective first andsecond slot ends, the first slot section having a width that is smallerthan a width of the second slot section.
 10. The capillary threadingtool of claim 9, further comprising an inclined surface formed at thefirst slot end, the inclined surface sloping from the first slot endtoward the second slot section.
 11. The capillary threading tool ofclaim 10 wherein the inclined surface comprises an inclined plane. 12.The capillary threading tool of claim 9 wherein the first and secondslot ends are substantially aligned with each other.
 13. A method ofthreading a bond wire though a capillary tube of a wire bond machinehaving a guide tube positioned above the capillary tube to form a gaptherebetween, the method comprising: placing a capillary threading toolin the gap, the capillary threading tool having a slot extending betweenthe guide tube and the capillary tube and being open at one end andclosed at an other end, the capillary threading tool being positioned sothat the closed end of the slot is substantially aligned with thecapillary tube; and threading the bond wire into the guide tube so thatthe end of the slot serves as a guide surface for guiding the bond wireinto the capillary tube.
 14. The method of claim 13 wherein thecapillary threading tool further comprises an inclined surface formed atthe end of the slot sloping inwardly toward the closed end of the slot,and wherein the act of placing the capillary threading tool in the gapcomprises placing the capillary threading tool in the gap with a portionof the inclined surface positioned beneath the guide tube.
 15. Themethod of claim 13 wherein the slot of the capillary threading tool isdivided into upper and lower slot sections, and wherein the act ofplacing the capillary threading tool in the gap comprises placing thecapillary threading tool in the gap with the lower slot sectionstraddling the capillary tube.
 16. The method of claim 15 wherein theupper slot section has a width that is smaller than an outside diameterof the capillary tube, and wherein the act of placing the capillarythreading tool in the gap comprises placing the capillary threading toolin the gap with the upper slot section positioned above the capillarytube.
 17. The method of claim 15 wherein the act of placing thecapillary threading tool in the gap with the lower slot sectionstraddling the capillary tube comprises placing the capillary threadingtool in the gap with a closed end of the lower slot section contactingan outer surface of the capillary tube and a closed end of the upperslot section substantially aligned with the capillary tube.
 18. Themethod of claim 13 wherein the capillary tube is fastened to the wirebond machine with fasteners, wherein the capillary threading tool hasformed therein a transverse slot, and wherein the act of placing thecapillary threading tool in the gap comprises placing the capillarythreading tool in the gap with the fasteners in the transverse slot. 19.The method of claim 13 wherein the act of placing the capillarythreading tool in the gap comprises placing the capillary threading toolin the gap with a surface of the capillary threading tool in contactwith a surface of the wire bond machine and the closed end of the slotsubstantially aligned with the capillary tube.
 20. The method of claim13 wherein the act of placing the capillary threading tool in the gapcomprises placing the capillary threading tool in the gap with thecapillary threading tube substantially filling the gap.
 21. The methodof claim 13 wherein the capillary threading tool further comprises abody portion containing the slot and a handle projecting from the bodyportion, and wherein the act of placing the capillary threading tool inthe gap comprises grasping the handle and then manipulating the handleto place the body portion of the capillary threading tool in the gap.22. The method of claim 13 further comprising withdrawing the capillarythreading tube from the gap after the bond wire has been threadedthrough the capillary tube by straddling the bond wire with the slotwhile moving the capillary threading tool perpendicular to the bondwire.